In its over-the-counter form, iodine is used in a tincture, ointment or gel to disinfect the skin and prevent or treat infections. For example, you might apply a liquid tincture of iodine to a cut or scrape. Iodine kills bacteria that can cause an infection. This type of iodine is for topical use only. When used as a disinfectant, iodine is often combined with another ingredient called povidone, and you might see it listed in a product's ingredients as povidone-iodine.